The password you need to enter is the macOS administrator password for your computer.
If you have a Mac that has Touch ID functionality, you can also use your fingerprint to authenticate the installation as well.
When you install new software onto your Mac you will be asked for your macOS administrator name and password. macOS will ask for this password or passphrase during any installation process so that unauthorized changes can not be made to the system.
The user account you created when you set up macOS is also the computer's administrator. There may be additional administrator accounts created on the computer, depending on how it was set up. You need to enter an administrator name and password in order to proceed with the installation. If this password has been lost, you can search macOS Help for information on how to reset the Administrator password.